It's too soon to say if Russian scientists are the first people to reach the buried Antarctic lake, according to Valery Lukin, director of the Russian Antarctic program.

Lukin told Nature that the team still has to analyze data from a number of sensors monitoring the drilling.

"Only when I will have this I can say we penetrated," he said. "We want to be sure we have really reached the surface of Lake Vostok."

Lukin and his team are racing to beat U.S. and UK teams to be the first to drill into the Antarctic lake that has been sealed off from the world for 15 million years. The Russian team has been drilling since January 2 and has been progressing by about 1.75 m per day. On January 12, the team switched from a large ice-coring drill to a smaller thermal drill that is designed to melt through the final five to ten meters of ice. Media reports circulated that the team has reached the lake but Lukin said information on the exact depth of ice drilled and the levels of various fluids in the borehole needed to be checked before they confirm that they have reached the sublevel lake. The data may be processed as soon as tomorrow.

"As soon as we get it officially confirmed, this information will be disseminated among the international community," says Lukin.

Lake Vostok, which is about the size of Lake Ontario, is the largest lake on the Antarctic. It is buried underneath 4 km of ice and is estimated to be about 14 million years old. Scientists estimate that the water in the lake is currently 1 million years old.

Reaching the lake is important because it could be home to microbial life that has adapted to living in total darkness. Exploring such extreme environments like Lake Vostok could allow scientists to discover new life forms and whether life could exist in such extreme conditions elsewhere in the solar system. Any organisms discovered in the buried lake would be entirely new and have been left on their own without any interference for millennia.

The Russian team has been racing against Antarctica's brutal winter weather. Temperatures have already dropped below minus 49 degrees Fahrenheit. The majority of the drilling team has left the Vostok station and only two members remain to monitor the borehole.

Even if the Russian team has reached the lake they will have to wait until next season to test the ice from the deep borehole. The Russians will face competition from British and American teams who are positioned to start drilling in autumn 2012 and January 2013 respectively.